The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Dovetail Rotor Poles in Synchronous Permanent Magnet and Reluctance Machines

Jere Kolehmainen

Doctoral dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the School of Electrical Engineering for public examination and debate in Auditorium S1 at the Aalto University School of Electrical Engineering (Espoo, Finland) on the 9th of September 2011 at 12 noon.

Overview in PDF format (ISBN 978-952-60-4195-7)   [4258 KB]
Dissertation is also available in print (ISBN 978-952-60-4194-0)

Abstract

Robust synchronous permanent magnet and reluctance machine designs are developed. In the designs, the rotor structure is simple and strong and the leakage flux is relatively small. For the new design solution, a dovetail form-blocked rotor structure, specific analyzing principles are also developed.

The dovetail designs are shown to be good solutions with their lower leakage flux and at least the same strength against centrifugal forces as the conventional rotor solutions. The compared conventional solutions considered have inseparable rotor sheets in which the parts of the rotor are kept still by using bridges between them. In the dovetail rotor, the forms of the rotor parts keep them together and no bridges between them are needed for support. The simplicity of the dovetail solution has also been kept the same or better. In addition, the manufacturing method is the same for both solutions. The dovetail design can also be used for saving the magnetic material of permanent magnet synchronous machines because it has a smaller leakage flux than the conventional V-shaped designs with supporting bridges.

The problem of how to compare the dovetail designs to the conventional ones is considered in depth. The strength of the dovetail structure has to be defined in a different way than in the conventional design with supporting bridges. In bridge-fixed design, the strength of the bridges is critical for rotor durability but in the dovetail design wider areas of the rotor affect the strength of the rotor. However, the basic electrical properties could be defined with the same method. Additional methods for defining the electrical properties of dovetail designs are also considered. One method is that the load angle can be defined only from the forms of phase currents in delta-connected synchronous machines and phase voltage and current in star-connected synchronous machines. The load angles defined are successfully used to find a good model for the test results. The other method is to view the normalized local torque density in the air gap as a function of time.

In this work, several dovetail synchronous reluctance and permanent magnet machines are designed, manufactured, tested, and analyzed. The design, manufacturing, testing, and analysis methods are defined and developed especially for dovetail designs.

This thesis consists of an overview and of the following 8 publications:

  1. J. Kolehmainen. 2006. Finite element analysis of two PM-motors with buried magnets. In: Sławomir Wiak, Maria Dems, and Krzysztof Komęza (editors). Recent Developments of Electrical Drives. Best Papers from the 16th International Conference on Electrical Machines (ICEM 2004). Cracow, Poland. 5-8 September 2004. Dordrecht, The Netherlands. Springer. Pages 51-58. ISBN 1-4020-4534-4. © 2006 by author and © 2006 Springer Science+Business Media. By permission.
  2. Jere Kolehmainen and Jouni Ikäheimo. 2008. Motors with buried magnets for medium-speed applications. IEEE Transactions on Energy Conversion, volume 23, number 1, pages 86-91. © 2008 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  3. Jere Kolehmainen. 2008. Machine with a rotor structure supported only by buried magnets. In: Sławomir Wiak, Andrzej Krawczyk, and Ivo Dolezel (editors). Advanced Computer Techniques in Applied Electromagnetics. 13th International Symposium on Electromagnetic Fields in Mechatronics, Electrical and Electronic Engineering (ISEF 2007). Prague, Czech Republic. 13-15 September 2007. Amsterdam, The Netherlands. IOS Press. Studies in Applied Electromagnetics and Mechanics, volume 30, pages 240-246. ISBN 978-1-58603-895-3. © 2008 by author.
  4. Jere Kolehmainen. 2010. Optimal dovetail permanent magnet rotor solutions for various pole numbers. IEEE Transactions on Industrial Electronics, volume 57, number 1, pages 70-77. © 2010 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  5. Jere Kolehmainen. 2010. Permanent magnets synchronous machine with rotor poles supported by magnets. In: Proceedings of the 19th International Conference on Electrical Machines (ICEM 2010). Rome, Italy. 6-8 September 2010. Piscataway, NJ, USA. IEEE. Paper RF-005207. 6 pages. ISBN 978-1-4244-4175-4. © 2010 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  6. Jere Kolehmainen. 2010. Synchronous reluctance motor with form blocked rotor. IEEE Transactions on Energy Conversion, volume 25, number 2, pages 450-456. © 2010 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  7. Sami Ruoho, Jere Kolehmainen, Jouni Ikäheimo, and Antero Arkkio. 2009. Demagnetization testing for a mixed-grade dovetail permanent-magnet machine. IEEE Transactions on Magnetics, volume 45, number 9, pages 3284-3289. © 2009 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  8. Sami Ruoho, Jere Kolehmainen, Jouni Ikäheimo, and Antero Arkkio. 2010. Interdependence of demagnetization, loading, and temperature rise in a permanent-magnet synchronous motor. IEEE Transactions on Magnetics, volume 46, number 3, pages 949-953. © 2010 Institute of Electrical and Electronics Engineers (IEEE). By permission.

Errata of publications 2, 3 and 6

Keywords: electromagnetic analysis, strength analysis, permanent magnet machines, synchronous reluctance machines

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Last update 2011-08-15